The proposed research will investigate the role of a closely related group of enzymes in the mechanisms of oncogenic transfromation and growth control in cultured cells. This group of enzymes includes the nonspecific carboxylesterases, nonspecific amidases, and several specific proteases. The following methods are proposed: 1. Determination of these enzyme activities in subcellular fractions of "normal" and virally transformed cultured cells. 2. isolation and characterization of any esterases and aaidases that are found specifically in transformed or growing cells. 3. Determination of the variation of these enzyme activities with temperature change in transformed cells that have a temperature-sensitive mutation in the transformed phenotype. 4. Islation of mutants lacking these enzyme activities and studies of the growth and transformation characteristics of the mutants. 5. Determintion of the activities of these enzymes during productive infection by viruses. 6. Determination of the activities of these enzymes throughout the cell cycle of normal cells. The proposed work includes the preparation of several fluorogenic substrates that are expected to make possible very sensitive fluorescent assays and to induce fluorochromasia in cultured cells. These studies should increase our understanding of the phenomenon of fluorochromasia and further develop it as a technique in cell biology.